Science lesson plan · 8th grade (Year 9 in England) · 45 minutes
Use twins and clones to separate genes from environment
Cells, genetics and evolution
CCSS NGSS.MS-LS1-5CCSS NGSS.MS-LS3-2CCSS NGSS.SEP 7England: KS3 Biology: Inheritance, chromosomes, DNA and genesEngland: GCSE Combined Science: Inheritance, variation and evolution
Objective and success criteria
Students will: Use twins and clones to separate genes from environment.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Genes, alleles, genotypes and phenotypes; Continuous and discontinuous variation
Leads to: the next skill in this area.
Materials: Microscope images or slides, Cell diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Genes, alleles, genotypes and phenotypes; Continuous and discontinuous variation). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Which word means: the alleles an organism has, written like Bb? (dominant / recessive / genotype / allele) → genotypePrompt: “Geno-” is about the genes you carry; “pheno-” is about what you see.
- Is this continuous or discontinuous variation: Rhesus blood type (positive or negative)? (continuous / discontinuous) → discontinuousPrompt: Can it have any value, or only a few set categories?
- An organism has the genotype bb. How is this genotype described? (homozygous dominant / heterozygous / homozygous recessive) → homozygous recessivePrompt: Capital letters stand for dominant alleles.
Hook · 5 min
- Show a microscope image of cells and ask what students think they are looking at.
- Share the objective: Use twins and clones to separate genes from environment. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 49 cm, shade 32 cm. What can you conclude?
- Step 1: Same genes, different conditions: the 17 cm difference is environmental.
- Step 2: So the answer is: The difference in height was caused by the environment (light).
- Answer: The difference in height was caused by the environment (light).
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 40 cm, shade 25 cm. What can you conclude? (The results show light has no effect. / Height is controlled only by genes. / The plants in the shade had different genes. / The difference in height was caused by the environment (light).) → The difference in height was caused by the environment (light).Prompt: Clones have identical genes.
- Two rabbits from the same litter are fed different diets and grow to different sizes. Why can we not be sure the difference is only due to diet? (Rabbits do not have genes / Diet never affects size / Brothers and sisters do not have identical genes / The rabbits are clones) → Brothers and sisters do not have identical genesPrompt: Only identical twins and clones share all their genes.
You do: independent practice · 10 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 38 cm, shade 24 cm. What can you conclude? (The difference in height was caused by the environment (light). / The plants in the shade had different genes. / The results show light has no effect. / Height is controlled only by genes.) → The difference in height was caused by the environment (light).Prompt: Clones have identical genes.
- Identical twins raised apart often have very similar blood groups and eye colour but different body mass. What does this suggest? (All three are purely environmental / Body mass is purely genetic / Blood group is genetic; body mass is affected a lot by environment / Twins have different genes) → Blood group is genetic; body mass is affected a lot by environmentPrompt: Identical twins share all their genes.
Watch out for
- Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
- Remembering facts without the reason: ask "why?" and "what is the evidence?"
Support and stretch
Support
- Review first: Genes, alleles, genotypes and phenotypes.
- Use concrete materials: microscope images or slides.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-8.
Free lesson plan from eurekami.com/lesson-plan-builder